I'm in a similar situation with a lost password.
The previous administrator of cpanel installed it (cpanel), and doesnt remember the password.
I have root access to the computer, but cant find the email address associated with the "manager" account, so every time the password is reset, I am unable to intercept the email.
Could you give more detailed instructions on how to "login to WHM" ?
Or is there some documentation on which files to modify to reset the password you could direct me to?